Gypsum board is widely used in both residential and commercial construction for interior walls and ceilings. One reason for this is that gypsum board is lighter than masonry or concrete walls and can eliminate the need for costly footers or foundation modifications. Gypsum board is also considered well-suited for construction requiring cost-effectiveness, fire resistance, and durability.
Gypsum board, however, has found limited utility for exterior applications due to concerns with weather resistance, for example, mold and moisture resistance. One kind of gypsum board has a sandwich construction of fiberglass facers and gypsum filling. Especially for demanding exterior construction applications, it would be preferable to apply a water-resistant coating on the top fiberglass facer.